URGENT - how to check person is married in Malaysia

I am from Singapore. My brother has a vietnamese girlfriend and they are getting married in Singapore in a few weeks time. She declared she is a single woman. A Malaysian friend told me she is very sure this vietnamese girl is a married woman in Malaysia but refused to provide further information.

Please advise how I or my brother can go about checking if this vietnamese girl is married in Malaysia or not. We have her passport number and her vietnamese ID number.